Method of making brominated indigoes



Pwmnted (M. W, 1922..

r61 I U f C. J. STROSACKER AND H. J. RUPRIGHT.

METHOD OF MAKING BROMINATED INDIGOES.

APPLICATION FILED SEPT. 1, 1.920.

YHALWLMHW Patented Unto Th3, 'W

CHARLES d". STRUSACKER AND HUWARD J. RUTRTGHT, 01E MIDLAND, MTGEEIGAN,

ASSIGNORS TO THE DOW CHEMICAL CUMEPAINY, F MIDLAND, MICHIGAN, A COR- PORATIUN 01E MICHIGAN.

rnrn'on or tannins nnonrna'rnn rnnreons.

, Application filed September 1, 1920. Serial No. 40?,523.

To all whomit may concern.

Be it known that-we, CHARLiis .Srnd

SAGKER andl HOWARD J. RUPBIGHT, citizens of the United States, and residents of Mid- 5 land,.county of Midland, State of Michigan,

have jointly invented anew anduseful l[m.

provement in'Methods ofMakiiig Brominated lndigoes, of which the followingfis' a specification, the principle of the invention being herein explained and thebestymode in which we have contemplated applying-that principle, so as to distinguish it from other :inventions.

The bromination of indigo, especially where the higher bromine substitution prodnets are desired, has'always heretofore'been regarded as presenting peculiar difficulties or at least has so been represented, particularly in the patent literature. Thus, ithas 2o always apparently been regardedas essen- I elevated temperatures, on pressures, or both.

. The present reference istof the direct bromination-"of indigo in contradistinction to the introduction of the halogen in nuclei or radicals from which the indigo is subsequently syntheticallyprepared. i

l Tn contradistinction to the prevailing difficult and involved methods, we have discovered that it is possible to directly react upon I the dry indi 0 with bromine at atmospheric pressure an at a temperature not above 80 or- 90 (1., all of the known bromine substitution products i. e. mono-, di-, tri-, tetra-., pentaand-hex'abrom indigo being readily prepared by thismethod and with equal ease and facility, theonly difference in requirements for obtaining the different derivatives being i the proper proportioning of the amount of bromine utilized. The invention accordingly consists of the stepshereinafter fully described and particularly pointed out in the claims, it being understood that the annexed drawing and following description illustrate merely one of the several ways in which the invention may be embodied. V

In said annexed drawing The single figure there appearing is a diagrammatic representation of an apparatus suitable for the carrying out of our present Improved method of brominating indigo.

Asshown in 'the drawing in question, the reaction chamber 1 consists of an ordinary sheet steel tumbler revolving upon trunnions 2 and 3 and containing a number of .iron balls 4., said tumbler being jacketed to permit the circulation of hot water or other heating medium around the same. Such heatin medium is designed to be supplied throug connections- 6 leading through the trunnion 2. Tn view'of the moderate temperatures required, as hereinafter set forth, such heating may be accomplished by simply revolving the tumbler in a more, or less open water bath. i I

The tumbler is-provided in its side with a manhole opening 7 having a suitable closure, through. which opening the dry indigo maybe charged; Said tumbler also is provided with a connection 8 through trunnion 3, through which liquid bromine may be similarly supplied to its interior. Connected with the interior of the tumbler through v this same trunnion 3 is a reflux condenser 9 of usual construction, connected at its discharge end with an absorber 10 adapted to contain caustic soda for the purpose presently to be described.

I In the operation of the foregoing apparatus to carry on our improved method of brominating indigo, the dry indigo as already indicated, is charged into the tumbler .through the opening 7, the latter closed and the tumbler then revolved for a short time, as a result of which the indigo is more or less finely pulverized by the action of the balls 4, Thereupon the liquid bromine is started in through the connection provided for the purpose, the total charge being added at the start and as speedily as possible. Then the charge is heated up as fast as the reaction will permit (no pressure being allowed to build upin the reaction chamber or tumbler) until a temperature of to C. is obtained, such temperatures refer, ring to the water bath or circulating liquid whereby the tumbler is heated. The gas coming from the tumblerpasses through the reflux condenser which serves to returnto said tumbler the bromine driven off, while the hydrobromic acid formed as a result of the reaction goes on to be absorbed in the caustic soda in the absorber.

Tt will be understood that during the operation just described the tumbler continues i to be revolved, the above mentioned temperature being maintained from 6 to 7 hours, being increased'gradually in the latter portion of such period from 60 to 80 (3. and then carried up to 90 C., Where it is held for from 7 to 9 hours longer.

The foregoing procedure obtains whichever of the substitutions it is desired to make, the degree of substitution being con- 1O The ratio of bromine charged, in order to trolled by the amount of bromide-added.

. charge is thoroughly uniform and ground off from the sides of the tumbler. Sodium bisulphite is then added and the grinding continued at room temperature for several hours, whereby all of the bromine combined with the product in an unstable form is removed and the product itself at the same 1 time is ground to a very high degree of fineness.

The charge is finally transferred to a suitable container and given a strong acid boil With hydrochloric acid for several hours, after which the product is filtered, washed with water and made up to the customary percentage paste for the trade, or else formed in cakes ordried to form a powder, as the case may be. The bromine recovered in the absorber as sodium bromide may be reconverted into liquid bromine for further use, and since we are able to thus recover over 90% of that portion of the original charge of bromine not combined with the product, it will be evident that a high degree of economyv is eflected in this respect. \Ve also obtain by the processes described above efliciencies in the case of each product named of above 90% based upon the dryindigo charg'ed.

Other-modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

We therefore particularly point out and distinctly claim as our invention 1. The metliod of brominating indigo, which consists in reacting directly on the same, dry, in the absence of any diluent or other reagent, with bromine in amount from 15% to 25% in excess of the theoretical to form the desired substitution product, the reaction being carried on at a temperature of from 50 to. 90 C. and under approximately atmospheric pressure.

2. The method of brominating indigo, which consists in reacting directly on the same, dry, in the absence of any diluent or other reagent. with bromine in amount from 15% to 25% in excess of the theoretical to form a mono-brom to hexa-brom substitution product as desired, the reaction being carried on initially at a temperature of from 50 to 60 C. and then gradually increased to approximately 90 C. all under approximately atmospheric pressure. a

3. The method of brominating indigo, which consists in reacting directly on the same, dry, in the absence of any diluent or other reagent, with bromine in amount from 15% to 25% in excess of the theoretical to form a mono-brom. to hexa-brom substitu tion product as desired, the reaction being carried on for six to seven hours at from 50 to 60 C., then gradually increased to approximately 90, such last mentioned temperature being maintained for seven to nine hours, all under approximately atmospheric pressure.

4. In a method of brominating indigo, the steps which consist in adding directly to the same, in dry finely ground condition and in the absence of any diluent or other reagent, a quantity of liquid bromine in amount from 15 per cent to 25 per cent in excess of the theoretical to form the desired substitution product, grinding together the two ingredients, and gradually heating the resulting mixture to a temperature of from 50 to 60 C., all under approximately at mospheric pressure.

5. In a method of brominating indigo, the steps which consist in adding directly to the same, in dry finely ground condition and in the absence of any diluent or other reagent, a quantity of liquid bromine in amount from 15 per cent to 25 per cent in excess of the theoretical to form the desired substitution product, grinding together the two ingredients, and heating the resulting mixture as fast as the reaction will permit first to from 50 to 60 C. and then to approximately 90 C.

6. In a method of brominating indigo, the steps which consist in adding directly to the same, in dry finely ground condition and in the absence of any diluent or other reagent, a quantity of liquid bromine in amount from 15 per cent to 25 per cent in excess of the theoretical to form the desired substitution product, the total quantity of bromine being added at once, grindin together the two ingredients and gradual y heating the resultmg mixture to a temperature of from 50 to 90 0., all under approximately atmospheric pressure.

7. In a method of brominating indigo, the steps which consist in adding directly to the rasneoe same. in dry finely ground condition and in the absence of any diluent or other reagent, aquantity of liquid bromine in amount from 15 per cent to per cent ih excess of the theoretical to form the desired substitution product, the total quantity of bromine being added at once, grinding together the two ingredients, and heating the resulting mixture as fast as the reaction will permit first to from 50 to 60 C. and then to approximately 90 G. r

8. In a method of brominating indigo, the steps which consist in adding directly to the same, in dry finely ground condition and in the absence of any diluent or other reaent, a quantity of liquid bromine in amount rom 15 per cent to 25 per cent in excess of the theoretical to form the desired substitution product, the total quantity of bromine being added at once, grinding together the two ingredients, andheating the resulting mixture as fast as the reaction will permit first to from 50 to 60 (1., then to approximately 90 O, neutralizing the charge, and then adding sodium bisulphite, the grinding being continued during the two last-named steps. 9. in a method of brominating indigo, the steps which consist in adding directly to the same, in dryfinely ground condition and inthe absence of any diluent or other reagent, a quantity of liquid bromine in amount from 15 per cent to 25 per cent in excess of the theoretical to form the desired substitution product, the total quantity of bromine being added at once, grinding together the two ingredients, and heating, the resulting mixture as fast as the reaction will permit first to from 50 to 60 0., then to approximately 90 (3., neutralizing the charge with caustic soda, and then adding sodium bisulphite, the grinding being continued during the two last-named steps.

Signed by us, this 2nd day of August,

CHARLES J. STROSACKER.

HOWARD J. RUPRIGHT. 

